Simscape™ 3
Getting Started
Guide
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Simscape™ Getting Started Guide
© COPYRIGHT 2007–20 10 by The MathWorks, Inc.
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Revision History
September 2007 Online only New for Version 2.0 (Release 2007b)
March 2008 Online only Revised for Version 2.1 (Release 2008a)
October 2008 Online only Revised for Version 3.0 (Release 2008b)
March 2009 Online only Revised for Version 3.1 (Release 2009a)
September 2009 Online only Revised for Version 3.2 (Release 2009b)
March 2010 Online only Revised for Version 3.3 (Release 2010a)
Introduction to Simscape Software
1
Product Overview ................................. 1-2
Product Definition
Simscape Block Libraries
Physical Modeling Product Family
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Contents
Prerequisites
Background Knowledge
Required Products
Opening Simscape Libraries
Creating a New Simscape Model
Working with a Simscape Demo Model
About This Tutorial
Exploring the Model
Running the Model
Modifying the Model
Learning M ore
Next Steps
Product Help
The MathWorks Online
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v
vi Contents
Introduction to Simscape
Software
• “Product Overview” on page 1-2
• “Prerequisites” on page 1-6
• “Opening Simscape Libraries” on page 1-7
• “Creating a New Simscape Model” on page 1-8
• “Working with a Simscape Demo Model” on page 1-11
1
• “Learning More” on page 1-21
1 Introduction to Simscape™ Software
Product Overview
In this section...
“Product Definition” on page 1-2
“Simscape Block Libraries” on page 1-2
“Physical Modeling Product Family” on page 1-4
Product Definition
Simscape™ software extends the Simulink®product line with tools for
modeling and simulating multidomain physical systems, such as those with
mechanical, hydraulic, pneumatic, thermal, electrical, and electromagnetic
components. Unlike other Simulink blocks, which represent mathematical
operations or operate on signals, Simscape blocks represent physical
components or relationships directly. With Simscape blocks, you build a
model of a system just as you would assemble a physical system.
1-2
Simscape models employ a Physical Network approach to model building:
components (blocks) corresponding to physical elements such as pumps,
motors, and op-amps, are joined by lines corresponding to the physical
connections that transmit power. This approach lets you describe the
physical structure of a system rather than the underlying mathematics.
From your model, which closely resembles a schematic, Simscape technology
automatically constructs equations that characterize the behavior of the
system. These equations are integrated with the rest of the Simulink model.
Simscape software runs within the Simulink environment and interfaces
seamlessly with the rest of Simulink product family and with the MATLAB
technical computing environment.
Simscape Block Libraries
Simscape Foundation libraries contain a comprehensive set of basic elements
and building blocks, such as:
• Mechanical building blocks for representing one-dimensional translational
and rotational motion
®
Product Overview
• Electrical building blocks for representing electrical components and
circuits
• Magnetic building blocks that represent electromagnetic components
• Hydraulic building blocks that model fundamental hydraulic effects and
can b e combined to create more complex hydraulic components
• Pneumatic building blocks that model fundamental pneumatic effects
based on the ideal gas law
• Thermal building blocks that model fundamental thermal effects
• Physical Signals block library that lets you perform math operations on
physical signals, and graphically enter e quations inside the physical
network
Using the elements contained in these Foundation libraries, you can create
more complex components that span different physical domains. You can
then group this assembly of blocks into a subsystem and parameterize it to
reuse and share these components.
Shown below is a Simscape model of a DC motor that acco unts for friction and
includes electrical and mechanical components. You can easily match the
model to the motor illustration on the right. The model contains two electrical
ports, corresponding to the V+ and V- electric terminals of the motor, and two
mechanical rotational ports, C and R, corresponding to the motor case and
rotor, respectively. It is built of Simscape foundation blocks. You can use
this model to create a masked subsystem of a DC motor, to reuse and share
in electric diagrams.
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1 Introduction to Simscape™ Software
In addition to Foundation libraries, there is also a Simscape U t il ities lib rary,
which contains utility blocks , such as:
1-4
• Solver Configuration block, which contains parameters relevant to
numerical algorithms for Simscape simulations. Each Simscape diagram
(or each topologically distinct physical network in a diagram) must contain
a Solver Configuration block.
• Simulink-PS Converter block and PS-Simulink Converter block, to connect
Simscape and Simulink blocks. Use the Simulink-PS Converter block to
connect Simulink outports to Physical Signal inports. U se the PS-Simulink
Converter block to connect Physical Signal outports to Simulink inports.
For examples of using these blocks in a Simscape model, see the following
section, “Working with a Simscape Demo Model” on page 1-11.
Physical Modeling Product Family
Simscape functions and utilities support functionality common to other
Simulink products that use physical connections between their blocks.
Simscape serves as the platform product for these add-on products of the
Physical Modeling family:
• SimHydraulics
®
, for modeling and simulating hydraulic systems
Product Overview
• SimDriveline™, for modeling and simulating powertrain systems
• SimMechanics™, for modeling and simulating general mechanical systems
®
• SimElectronics
, for modeling and simulating electromechanical and
electronic systems
The Physical Modeling product family also contains SimPowerSystems™,
for modeling and simulating electrical power systems. Use these products
together to model physical systems in the Simulink environment.
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1 Introduction to Simscape™ Software
Prerequisites
In this section...
“Background Knowledge” on page 1-6
“Required Products” on page 1-6
Background Knowledge
This Getting Started guide requires that you have some experience with
modeling physical systems, as well as with building and running models in
the Simulink environment.
Required Products
Simscape software requires these products:
• MATLAB
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• Simulink
Opening Simscape Libraries
Simscape softw are is part of your MATLAB installation.
Opening Simscape™ Libraries
To open Simscape block libraries, type
Window to display the Simulink Library Browser, and then expand the
Simscape entry in the contents tree.
simulink in the MATLAB Command
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1 Introduction to Simscape™ Software
Creating a New Simscape Model
Simscape models require certain blocks to be present in the model
configuration, such as a Solver block, or domain-specific reference blocks.
Other blocks, although not required, are highly likely to be needed, such as
Simulink-PS Converter and PS-Simulink Converter blocks. An easy way to
start a new Simscape model is by using the
ssc_new command.
When you type
opens the main Simscape library and creates a new model prepopulated with
certain blocks, as shown in t he following illustration.
ssc_new at the MATLAB Command prompt, the software
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Creating a New Simscape™ Model
By default, the model name is not specified, the model contains a Solver
Configuration block with the default solver set to
ode15s,aSimulink-PS
Converter block, and a PS-Simulink Converter block connected to a Scope
block.
You can use the
ssc_new command arguments to specify the model name, add
a domain-specific reference block, and change the default solver. See the
ssc_new command reference page for details. For example, typing
ssc_new('rotor1','rotational','ode23t')
creates the following model.
rusing
Afte
eded, and adding other blocks from the Simscape libraries.
as ne
electrical models, you can also use the Creating A New Circuit demo as a
For
plate for a new model. This demo also opens an Electrical Starter Palette,
tem
ch contains links to the most often used electrical components. Open the
whi
obytyping
dem
le > Save As to save it under the desired model name. Then delete the
Fi
ssc_new, continue developing your model by copying the blocks,
ssc_new_elec in the MATLAB Com mand Window and use
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1 Introduction to Simscape™ Software
unwanted components and add new ones from the Electrical Starter Palette
and from Simscape libraries.
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Working with a Simscape Demo Mod el
In this section...
“About This Tutorial” on page 1-11
“Exploring the Model” on page 1-12
“Running the Model” on page 1-14
“Modifying the Model” on page 1-15
About This Tutorial
Thistutorialprovidesyouwithhands-onexperienceofusingSimscape
software. You will open a d emo model, examine how it is built, and run the
simulation. You will then perform simple modifications of the demo and view
their effect on the simulation results.
The Permanent Magnet DC Motor demo shows how Simscape models can
simulate system s that span electrical and mechanical domains. In this demo,
you learn how to model physical components with Simscape blocks, connect
them into a realistic model, use Simulink blocks as well, and then simulate
and modify a motor model.
Working with a Simscape™ Demo Model
The model is based on a Faulhaber Series 0615 DC-Micromotor. For the 1.5V
variant, equivalent circuit parameters are given as:
Rotor resistance R=3.9 Oh ms
Rotor inductance L=12mH
Back emf constant K=0.072mV/rpm
Rotor inertia J=0.01gcm^2
Friction torque Mr=0.02mNm
The model uses these parameters to verify manufacturer-quoted no-load
speed, no-load current, and stall torque, which are:
No-load speed = 19,100rpm
No-load current = 0.03A
Stall torque = 0.24mNm
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1 Introduction to Simscape™ Software
You can use the model to a ssess motor performance in a given application by
adding the requisite mechanical load model.
Exploring the Model
1 To open the Permanent Magnet DC Motor demo, type ssc_dcmotor in
the MATLAB Command Window.
1-12
Main Model Window
The main mo del window contains a DC Motor subsystem with two electrical
and two mechanical rotational ports.
The electrical ports connect to the electrical circuit, which consists of an
Electrical Reference block, representing an electrical ground, a 1.5 V DC
voltage source, and a current sensor. The current sensor connects, through
a PS-Simulink Converter block, to a Simulink scope labeled Motor Current.
Working with a Simscape™ Demo Model
On the mechanical side, a Mechanical Rotational Reference block
represents a reference point for the other elements. An ideal rotational
motion sensor connects, through a PS-Simulink Converter block, to a
Simulink scope labeled RPM.
The motor load is represented by an Ideal Torque Source block, which on
onesideconnectstoaMechanicalRotational Reference b lock, and on the
other side to the motor shaft. A regular Simulink Step source provides
the control signal. A Simulink-PS Converter block converts the control
signal into a physical signal and applies it to the control port of the Ideal
Torque Source block.
The diagram also contains a Solver Configuration block, w hich is required
in any Simscape model. It contains parameters relevant to numerical
algorithms for Simscape simulations.
2 Double-click the DC Motor subsystem to open it.
DC Motor Subsystem
The motor consists of an electrical circuit and a mechanical circuit,
connected by the Rotational Electromechanical Converter block. The
electrical circuit consists of a Rotor Resistance block and an Inductance
block L. It contains two electrical ports, corresponding to the V+ and
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1 Introduction to Simscape™ Software
V- electric terminals of the motor. The mechanical circuit contains a
Rotational Friction block, Motor Inertia J, and two mechanical rotational
ports, C and R, corresponding to the motor case and rotor, respectively.
Notice how the C and R ports of the Friction block and the Rotational
Electromechanical Converter block are connected to the C and R ports of
the motor, to preserve the correct direction of variables in the Physical
Network.
Running the Model
After you have reviewed the block diagram of the demo model, you can run
the simulation.
1 Double-click the Motor Current and RPM scopes to open them. During
simulation, these windows display the motor current and shaft speed,
respectively, as functions of time.
2 In the toolbar of the model window, click to start the simulation. The
Simscape solver evaluates the model, calculates the initial conditions, and
runs the simulation. This process might take a few seconds. The message
in the bottom-left corner of the model window provides the status.
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3 Examine the simulation results in the Motor Current and RPM scope
windows.
Working with a Simscape™ Demo Model
For the firs t 0.1 seconds, the mo tor has no external load, and the speed
builds up to the no-load value. Then at 0.1 seconds, the stall torque
is applied as a load to the motor shaft. Zooming in on the R PM and
Motor Current scopes shows that the model matches the manufacturer
parameters for no-load speed, no-load current, and stall torque.
Modifying the Model
After running the initial simulation, you can experiment with adjusting
various inputs and block parameters. Try the following adjustments:
1 Change the supply voltage.
2 Change the motor load.
Changing the Supply Voltage
Reduce the supply voltage to 1.25 volts (to simulate the battery running down)
and vary the load torque to find the maximum torque at this reduced voltage.
1 Double-click the 1.5V DC Voltage Source block. Set Constant voltage to
1.25 V.
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1 Introduction to Simscape™ Software
2 Run the simulation. Note the effect of reduced voltage on the no-load speed.
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Working with a Simscape™ Demo Model
3 Try varying the load torque to find the maximum torque at this reduced
voltage. Double-click the Step source block, enter different final values for
the input signal, and rerun the simulation.
The next illustration shows th e simulation results for Final value set to
-0.2e-3, which corresponds to (1.25/1.5)*0.24mNm,asthemagnitudeof
the torque-speed curve i s proportional to voltage for a DC motor.
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1 Introduction to Simscape™ Software
Changing the Motor Load
Replace the torque source with a simple mechanical load, for example, a fan,
forwhichthetorqueisdefinedby
Nm/(rad/s)^2.
alpha*speed^2,wherealpha is -1e-10
1-18
1 Delete the Step source and the Simulink-PS Converter block from the
model.
2 In the Simscape block library, open Foundation Library > Physical
Signals > Fu nctions.
3 Drag the PS Product block and the PS Gain b lock to the model window.
4 Connect the blocks as shown in the following illustration. To rotate a block,
select it and press Ctrl+R.
Working with a Simscape™ Demo Model
5 Double-click the Gain b lock to open its dialog box. Enter Gain value of
-1e-10 and click OK.
6 Run the simulation and assess motor performance with the new load.
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1 Introduction to Simscape™ Software
1-20
Learning More
In this section...
“Next Steps” on page 1-21
“Product Help” on page 1-21
“The MathWorks Online” on page 1-22
Next Steps
To take the next lesson on using the product, follow the steps in “Creating
a Simple Model” in the Simscape User’s Guide.Alsoseethefollowingtopics
to continue your exploration:
Learning More
For...
Rules of building m odels with
physical components
Variables available with each
domain
Block o
Overview of the simulation process “How Simscape Simulation Works”
Code generation “Generating Code”
Prod
Mor
desktop, click
pane.
Fo
List of blocks “Block Reference”
Advanced tutorials
More product demonstrations
What’s new in this product
rientation in a model
uct Help
e information is available with your product installation. In the MATLAB
for help, and then click the product name in the Contents
r...
See...
“Basic Principles of Modeling
Physical Networks”
“Variable Types”
“Direction of Variables ”
See...
Examples
Simscape Demos
Release Notes
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1 Introduction to Simscape™ Software
The MathWorks On
Point your Inter
information and
net browser to the MathWorks Web site for additional
support at http://www.mathworks .com/products/simscape/.
line
1-22
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